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Horizon · our Election Day forecast: polls, plus fundamentals like incumbency, fundraising and past results.

Pulse · polls only: where the races stand today, with no fundamentals and wider uncertainty.

What's the difference?

Colorado · 2026 forecast · Updated Oct 16, 2026

Who will control the Colorado State Senate?

17 of 35 seats are on the ballot; the others are elected in alternate years. 18 seats make a majority. 24 make the two-thirds supermajority that can override a veto.

Democrats are very likely to control the Colorado State Senate (>99%).

Democrats
>99%
chance of control
Republicans
<1%
Avg. D seats
23.680% range 22–24
Avg. R seats
11.480% range 11–13
Now
23 D · 12 R17 up this year

Chance Democrats win a two-thirds supermajority (24+ seats): 62%

23 D nowMarks: two-thirds supermajority for each party12 R now

Democrats are very likely to control the Colorado State Senate (>99%).

Democrats
>99%
chance of control
Republicans
<1%
Avg. D seats
23.180% range 21–24
Avg. R seats
11.980% range 11–14
Now
23 D · 12 R17 up this year

Chance Democrats win a two-thirds supermajority (24+ seats): 41%

23 D nowMarks: two-thirds supermajority for each party12 R now

18 for control
18 for control
  • Solid D
  • Likely D
  • Lean D
  • Toss-up
  • Lean R
  • Likely R
  • Solid R
  • Holdover, not up this year

Race ratings

All 17 races, grouped by the leader's chance of winning.

1 seat projected to flip: 1 R→D.

1 seat projected to flip: 1 R→D. 1 more is a toss-up that could change parties (flip risk).

Solid D10

Likely D1

Lean D1

Toss-up0

Lean R0

Likely R2

Solid R3

Solid D6

Likely D4

Lean D1

Toss-up1

Lean R0

Likely R2

Solid R3

Columns follow the chance of winning: Toss-up 40–60%, Lean 60–80%, Likely 80–95%, Solid 95%+. The square shows who holds the seat now (■ Democrats, ■ Republicans). flip: projected to change parties, in the color of the party favored to gain it. risk: a toss-up (40–60%) that could change parties. Faded: no major-party opponent.

The map

Each district colored by the leader's chance of winning. Hover for details; click for the race.

Colorado

Denver

  • Solid D
  • Likely D
  • Lean D
  • Toss-up
  • Lean R
  • Likely R
  • Solid R
  • Projected flip (stripes: party holding it now)

Seats to watch

The closest races (Lean or Toss-up, Horizon), and the seats most likely to change parties.

Closest races

SD-30Kevin LeungJohn CarsonD flipD flip74%Dem.76%Dem.

Most likely to flip

SD-30Kevin LeungJohn CarsonD flipD flip74%to flip76%to flip SD-3Aaron GutierrezDana CharlesFlip risk19%to flip40%to flip SD-4Justin KurthTeddy Collins8%to flip7%to flip SD-9William Delano Moses IIITerri Carver5%to flip12%to flip SD-15Janice MarchmanRob Woodward4%to flip11%to flip SD-11Tony ExumLevon Stilson2%to flip13%to flip SD-8Dylan RobertsCorey Marshall1%to flip9%to flip SD-24Kyle MullicaKevin Allen1%to flip8%to flip SD-27Tom SullivanDanielle Lammon1%to flip4%to flip SD-20Sheila LiederRichard Mancuso<1%to flip2%to flip

How this chamber is elected

Rules that shape these races and the forecast.

Staggered Senate

Senators serve four-year terms; about half the seats are on the ballot each election.

17 of 35 seats on the ballot; 18 holdovers (12 D, 6 R) serve until a later election.

How the odds have moved

Chance of winning control, by forecast date.

0%25%50%75%100%AugSepOctNovNov 3Democrats >99%Republicans <1%

Updated nightly. Each day is the current model run on the polls that had ended by then (how).

0%25%50%75%100%AugSepOctNovNov 3Democrats >99%Republicans <1%

Updated nightly. Each day is the current model run on the polls that had ended by then (how).

Every outcome we simulated

Democratic seats across 40,000 simulations. Darker bars: the middle 80%.

18 for D control →D two-thirds →1820222426
18 for D control →D two-thirds →1820222426

Every race

17 races, 1 without a contest between the major parties.

17 races
DistrictCandidatesChance of winning (D · R)Avg. marginRatingLeanPolls
SD-1
● Jamie Jeffery● Byron PeltonINC
<1%>99%
<1%>99%
R+36.2R+40.0Solid RSolid RR+45—
SD-3Flip risk
● Aaron Gutierrez● Dana Charles
81%19%
60%40%
D+6.4D+2.3Likely DToss-upR+4—
SD-4
● Justin Kurth● Teddy Collins
8%92%
7%93%
R+10.5R+14.5Likely RLikely RR+18—
SD-7
● No Democrat● Janice RichINC
Republican unopposedRepublican unopposed—Uncontested RUncontested RR+26—
SD-8
● Dylan RobertsINC● Corey Marshall
99%1%
91%9%
D+19.5D+13.4Solid DLikely DD+11—
SD-9
● William Delano Moses III● Terri Carver
5%95%
12%88%
R+13.0R+11.6Likely RLikely RR+16—
SD-11
● Tony ExumINC● Levon StilsonAlso: Janet Turner (L)
98%2%
87%13%
D+17.2D+10.8Solid DLikely DD+5—
SD-15
● Janice MarchmanINC● Rob Woodward
96%4%
89%11%
D+13.6D+11.6Solid DLikely DD+8—
SD-20
● Sheila Lieder● Richard Mancuso
>99%<1%
98%2%
D+24.4D+21.5Solid DSolid DD+17—
SD-22
● Monica Duran● Steve Harkess
>99%<1%
>99%<1%
D+41.8D+38.6Solid DSolid DD+34—
SD-24
● Kyle MullicaINC● Kevin Allen
99%1%
92%8%
D+19.5D+14.0Solid DLikely DD+9—
SD-25
● William LindstedtINC● Rich GuggenheimAlso: Mark Philip Bromley (I)
>99%<1%
99%1%
D+30.6D+28.4Solid DSolid DD+24—
SD-27
● Tom SullivanINC● Danielle LammonAlso: Michele Poague (L)
99%1%
96%4%
D+21.3D+17.9Solid DSolid DD+13—
SD-30D flipD flip
● Kevin Leung● John CarsonINC
74%26%
76%24%
D+4.8D+6.8Lean DLean DD+2—
SD-32
● Emily Sirota● Sydnnia Wulff
>99%<1%
>99%<1%
D+56.9D+55.6Solid DSolid DD+50—
SD-34
● Chela Garcia Irlando● Jack DausAlso: Jacob Luria (L)
>99%<1%
>99%<1%
D+64.3D+66.5Solid DSolid DD+62—
SD-35
● Duane Gurule● Rod PeltonINCAlso: Richard Graf (L), Travis Star Nelson (I)
<1%>99%
<1%>99%
R+34.3R+39.8Solid RSolid RR+44—

Lean: how much more Democratic (D+) or Republican (R+) the place voted for president than the nation (2024 weighted 75%, 2020 25%). Ratings follow the chance of winning: Toss-up 40–60%, Lean 60–80%, Likely 80–95%, Solid 95%+. INC = incumbent running. D flip / R flip: another party is favored (60% or more) over the party holding the seat now (hover for the chance it changes parties); Flip risk: the seat is a toss-up (40–60%).